1. Field of the Invention
This invention relates to a method of and an apparatus for performing operations in relation to a container sleeve, in particular to a rotary machine for packaging liquid in cartons.
2. Description of the Prior Art
U.S. Pat. No. 3,579,958 discloses a rotary packaging machine for automatically forming, filling and sealing carton sleeves. The machine includes a rotary spider that holds the sleeves upright in holding devices at the ends of its horizontal arms and advances them stepwise through various operating stations of the machine. Each holding device includes a mounting block attached to the end of a spider arm, and a generally U-shaped holder fixed to the block and consisting of a backing plate and a pair of side flanges extending normally outward from the plate. The holder embraces the sleeve and has a width and depth slightly larger than the outer horizontal dimensions of the open sleeve. The holder is designed for use with carton sleeves of similar cross-section but various lengths, such as half-pint, pint, and quart size cartons. A second such U-shaped holder is suspended by links from the block and can be swung from a position beneath the first holder for embracing the lower part of a larger size, for example the quart size, sleeve into an out-of-the-way position. A locking lip extends obliquely from one of the side flanges of each holder towards the other side flange thereof to lock and hold the sleeve in an open and upright position.
The stations of the machine are, in turn, a loading station, a bottom closure heating station, a bottom closure folding and sealing station, a top closure pre-breaking station, a filling station, a top closure heating station, a top closure folding and sealing station and a discharge station.
At the bottom closure folding and sealing station a vertical mandrel having a head of a cross-sectional dimension slightly less than the internal dimensions of the carton sleeve is lowered by an hydraulic cylinder through the sleeve until the lower surface of the head is at the level of the sleeve bottom closure sub-panels. The stroke of the mandrel is adjustable so that the lower end position of the lower surface of the head is adjustable depending upon the height of the carton sleeve. Also at this station are a lock member mounted on a yoke through which the mandrel extends, and a press head secured to the upper end of a vertically reciprocating rod of an hydraulic cylinder fixed to a platform beneath the mandrel. A pair of folding plates are pivotally mounted upon the platform and are operable by movement of the press head towards and away from the sleeve, as also are a pair of roller bars. The level of the platform is vertically adjustable to allow for the various heights of the sleeves.
At the filling station, the open-topped carton is filled with a controlled quantity of liquid. The station includes a supply tank, a filling stem, and a dispensing valve for controlling the flow of liquid to the carton. A carton-operated time-control switch comprises electrical circuits which actuate the dispensing valve and automatically shut it off after a prescribed period of time corresponding to the volume of flow desired.
Machine cycling means are provided for rotating the spider stepwise and for actuating and controlling the various mechanism at the operating station. This means includes an indexing device connected to the driving axle of the spider for rotating the same, and electric and pneumatic control circuits for actuating hydraulic cylinders and other mechanisms at the stations.
This prior machine has a number of disadvantages. Firstly, when changing from handling sleeves of one height to sleeves of another height, a considerable amount of adjustment is required at various stations, which necessitates a considerable degree of complication in the designs of the stations affected and a substantial loss of production time. Secondly, the locking lips of the holders are liable to distort or damage the sleeves. Thirdly, although it is obviously desirable that the head of the mandrel should fit as snugly into the sleeve interior as possible in order to promote accurate folding of the closure sub-panels, the slight looseness of the sleeve in the holder and the normally inherent tendency for it to move out of its rectangular state mean that the mandrel head has to be undesirably smaller in external cross-section than the internal cross-section of the sleeve, otherwise the descending mandrel engages the top edge of the sleeve and crushes it. Fourthly, on the one hand the sealing pressure of the press head upon the bottom closure sub-panels should be relatively high, but, on the other hand, the higher the pressure required, the larger and more costly will be the hydraulic apparatus for operating the mandrel. Fifthly, time control of filling of a container is often unreliable in respect of the volume actually supplied, which is liable to vary with the viscosity of the liquid for example. Sixthly, at the discharge station, cartons of various heights will have their bottoms at various levels, which would create problems for their reception by a discharge conveyor. Seventhly, there is the risk of the mandrel descending dangerously should the pressure fluid supporting the mandrel discharge inadvertently. Eighthly, the passing of the mandrel through the yoke would make it more difficult to maintain aseptic if the machine were to be an aseptic packaging machine. Ninthly, the drive system used in the machine leads to motion patterns which tend to produce shock and vibration.